The embodiment relates to a light emitting device, a method of manufacturing a light emitting device, a light emitting device package and a lighting system.
A light emitting device (LED) includes a p-n junction diode having a characteristic of converting electric energy into light energy. The p-n junction diode may be formed by combining group III-V elements of the periodic table. The LED may represent various colors by adjusting the compositional ratio of compound semiconductors.
When a forward voltage is applied to an LED, electrons of an n layer are combined with holes of a p layer, so that energy corresponding to an energy gap between a conduction band and a valance band may be released. The LED emits the energy as the light.
For instance, a nitride semiconductor represents superior thermal stability and wide band gap energy, so that the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. In particular, blue, green, and UV light emitting devices employing the nitride semiconductor have already been commercialized and extensively used.
A light emitting device may be classified into a lateral type and a vertical type according to the positions of an electrode.
The lateral-type light emitting device among light emitting devices according to the related art is formed in a structure in which a nitride semiconductor layer is formed on a substrate, and two electrode layers are disposed on the nitride semiconductor layer.
Meanwhile, the lateral-type light emitting device according to the related art has a great loss caused at the active layer able to emit light since mesa etching is performed over a large area. In order to compensate for the loss, various attempts are performed to ensure a wider active layer.
For example, according to the related art, there has been an attempt to secure a relatively larger area of an active layer by forming an electrode making contact with a nitride semiconductor layer in a through-electrode type to allow the electrode to be partially and electrically connected to the nitride semiconductor layer so that a removed area of the active area is reduced. However, the related art has a problem in reliability since an operating voltage VF is increased, and thus, the improvement is required.
In addition, according to the related art, the light extraction efficiency may be degraded due to the light absorption of the electrode layer.